1. Field of the Invention
The present invention relates to electrical connectors, and in particular to connectors for circuit cards used in a card-on-board installation. More particularly, the present invention is directed to card edge connectors that provide closely spaced contacts from multiple levels of the circuitry in the card or board.
2. Description of the Prior Art
Modern electronic devices use printed circuit boards to interconnect a number of electrical components. The circuit boards contain multiple levels of conductive circuitry which are formed in the pattern necessary to interconnect the components on those cards. Larger electronic devices require a number of circuit cards to accomplish their specified function. When a number of cards are used they are typically interconnected through the use of a backplane printed circuit board or motherboard. Each of the circuit cards, commonly known as daughter cards, are connected to the motherboard through a series of electrical contacts.
The electrical interconnection between printed circuit boards and the backplane or motherboard have typically been through the use of backplane contacts that connect with surface contacts on the circuit card. The connector on the motherboard is in turn connected to circuitry routed through the motherboard to accomplish the necessary function. An example of a connector according to this prior art technique is shown in U.S. Pat. No. 4,685,031 to Fife et al.
Prior art devices have also attempted to reduce the space occupied by printed circuit boards by mounting them at an angle. U.S. Pat. No. 4,756,694 illustrates this application.
The use of surface contacts on the circuit board requires that the electrical circuitry from lower layers of a multilayer circuit card be brought to the surface. This is typically accomplished through the use of vias or plated through holes. The use of these techniques to extend the circuitry to the card surface has a disadvantage of increasing the signal path length within the card and of reducing the connector density since the surface area available for connector contacts is limited. Finally, the use of present connector technology results in two or more contact interfaces which can have a detrimental effect on signal integrity and reliability of the interface. The two interfaces are first between the circuit card and the connector and second between the connector and the motherboard.
Thus, the technical problem solved by the present invention is the provision of a way to connect circuit cards to motherboards so that signal path length is minimized and the number of interfaces reduced.